This invention relates to voltage followers and gain cells, and more particularly, to voltage followers used in high-bandwidth low-voltage gain cells.
Differential circuits generate signals that are proportional to the algebraic difference between two input signals. These circuits produce an output signal only when differences exist between the input signals.
Ideally, the output signal of a differential circuit is not dependent on the magnitude of its input signals. However, when input signals are very xe2x80x9cweak,xe2x80x9d such signals can be so small that they cannot be processed reliably. Thus, when feeding xe2x80x9cweakxe2x80x9d input signals into a differential circuit, the xe2x80x9cweakxe2x80x9d input signals can be attenuated and the small-signal variations that can exist between these input signals cannot be detected. In other words, the information contained within the input signals and the algebraic difference between them can be lost.
Conceptually, signal amplifiers might be used to condition input signals before the differential circuit processes the input signals. If signal amplifiers are used, the signal amplifiers must be matched and the signal amplifiers must further preserve the information contained within the input signals. One drawback to using signal amplifiers is that the resulting circuit can have a limited bandwidth. Poles of the signal amplifiers can attenuate the input signals at high frequencies, which limit the bandwidth of the differential circuit.